Definition: You are given a question on human aging. You are also given 4 answer options (associated with "A", "B", "C", "D"), out of which only one is correct. You need to answer the question by selecting the correct option. You should only answer with the choice letter, not the whole answer.
Input: Normal memory seems to be improved by
(A)Aerobic exercise (B)Taking acetylcholine (C)Taking gingko (D)Increasing social contacts

A